Practice question

**Motion of charged particle perpendicular to uniform B** is circular because force F ⊥ v, no work done, speed constant, radius r = m v/(q B), period T = 2π m/(q B) independent of v. If v has component parallel to B, helical path results, pitch = v_parallel·T. tau = N I A B sin θ , θ = 90° to plane means sin 0° = 1 with normal. tau = 22 × 3 × 0.06 × 0.5 × 1 = 1.98 N m . Using F = q v B sinθ, F = I l B sinθ, B = μ₀ I/(2π r), B =